Fractionation of high Kappa number kraft pulps of the South African softwoods and sulfonating of coarse fibre enriched fraction for production of sack paper

摘要

The focus of this study was to investigate fractionation as a means to manufacture sack paper with uniform quality properties at increased refining energy efficiency compared to currently applied technologies. Kraft pulp produced at Kappa number approximately 85 was fractionated using a hydrocyclone and the coarse fibre enriched fraction was sulfonated. Sulfonation was carried out to enhance the refinability of the coarse fibre enriched fraction, evaluated using a PFI mill. The results indicate that the best fractionation can be achieved using feedstock consistency of 0.25% at volumetric reject ratio of 30%. As expected, sulfonation resulted in the coarse fibre enriched fraction responding more favourably during the refining/PFI beating process. For effective sulfonation, sodium sulfite dosage of 10% at a treatment time of 20 minutes was required. Measurement of the refining energy/PFI beating level required to achieve a target freeness of 550 ml CSF revealed that the sulfonated pulp can require 17% less beating energy compared to the unsul-fonated pulp.